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Hidden
Danger
By J. K. Tukra
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It is not
an uncommon story, a fit man in his 40s or 50s arrives
at medical clinic for his annual checkup and eventually
leaves with a clean bill of health. Soon afterward
he drops dead of a heart attack. Why didn’t
his test show some thing wrong? Researchers think
that they know the reasons.
Evidence is growing that not all the fatty deposits
found in coronary arteries are equally prone to
trigger heart attacks. Often the smallest, least
detectable plaques are the most dangerous, as their
tendency to burst, triggering the formation of a
clot that blocks a blood vessel. Doctors attending
the American College of Cardiology meeting in Atlanta
recently presented data suggesting that as many
as 80% of all heart attacks, not just the ones that
seem to strike out of the blue, are caused by this
so-called vulnerable plaque.
To learn more about these deadly deposits and how
they are changing the conventional wisdom on what
causes heart attacks, one of the leading researchers
in this field: Dr. Peter Libby, chief of cardiovascular
medicine at Brigham and Women’s Hospital in
Boston, compares the cross section of an artery
to a doughnut with a hole, where the doughnut is
the space where blood flows. “In the past,
we have studied just the hole,” he says. So
big plaques that appeared on the verge of plugging
the hole looked mighty dangerous, and many of them
are. But, Libby adds, “it is important to look
at the doughnut itself.”
Once doctors do that, they realize that there are
two main types of plaque: hard and soft. The soft
kind is the most vulnerable to rupturing without
warning. But what makes soft plaque doubly dangerous
is that it doesn’t always protrude into the
hole where the blood flows. Instead it is buried
in the arterial wall, or doughnut, where it is harder
to detect.
Some doctors are experimenting with ultrasound probes,
which they thread through the arteries to try to
locate this soft, vulnerable plaque. Others are
looking at magnetic resonance imaging and other
specialized scanning techniques that may highlight
the presence of vulnerable plaque.
In the mean time, researchers are focusing on ways
to make vulnerable plaque more stable. One promising
possibility: the increasingly popular class of cholesterol-lowering
drugs called statins, which seem to pull soft plaque
out of fatty deposits wherever it is located in
the artery, making it less likely to burst. Of course,
it never hurts to quit smoking, eat right and make
sure your blood pressure is under control, though,
if you don’t want your heart to surprise you.
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Blood
Flow and High-fat Meal
By R A Chan
While a lifetime of fatty meals can lead to a heart
attack, a study says that chowing down on just one high-fat
meal can interfere with blood flow to the heart in healthy
young men.
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In the study, 15 healthy men in their 20s
or early 30s consumed a shake containing a whopping 1,200
calories and 100 grams of fat--roughly the equivalent
of eating a fast-food meal plus dessert. All of the men
underwent a heart test and had blood samples taken before
and after consuming the liquid meal. The researchers,
led by Dr. Takeshi Hozuml of Osaka City University in
Japan, found that 5 hours after the high-fat meal, the
ability of heart arteries to expand and increase blood
flow to the muscle--a measure known as coronary flow reserve--dropped
by 18%.
In addition, five men underwent the same tests after consuming
a low-fat 1,200-calorie meal that contained only 10 grams
of fat. In that case, the men did not have a drop in coronary
flow reserve after consuming the meal, according to the
report in the April issue of the Annals of Internal Medicine.
The findings suggest that coronary microcirculation--the
tiny blood vessels that provide oxygen-rich blood to heart
muscle--can be impaired by a high-fat meal. Although the
study did not include people with heart disease, the results
could explain why those with heart disease-related chest
pain, known as angina, can have increased pain after a
high-fat meal. The pain of angina is thought to be due
to a reduction in blood flow to the heart.
The heart, the body's blood pumping organ, requires its
own blood supply to function properly. Coronary arteries
are the main blood vessels that supply the blood to the
heart, and if a blockage occurs the surrounding vessels
compensate by expanding in size to keep the proper amount
of blood flowing to the heart. Doctors have know that
a high-fat meals, which increase the amount of fatty substances
in the blood such as triglycerides, can over time lead
to artery clogging and eventually heart attacks. In the
new study, the investigators found that triglyceride levels
jumped from 140 milligrams per deciliter of blood (mg/dL)
after the high-fat meal, but only 10 mg/dL after the low-fat
meal. While the researchers were not able to determine
if the increase in triglyceride levels was responsible
for the decrease in the heart's blood flow reserve, the
authors say the findings suggest implications for patients
with heart disease. |
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